大涝坝地区苏维依组滨浅湖砂坝沉积精细刻画

Detailed Characterization of the Shore-shallow Lacustrine Sand Bar of Suweiyi Formation in Dalaoba Area, Tarim Basin, China

滨浅湖砂坝沉积是一种重要的陆相油气储集体,其空间展布多与湖岸线平行或低角度相交。大涝坝地区苏维依组沉积地层,具有明显的滨浅湖砂坝沉积特点,但其空间展布特征却与众不同。通过岩心观察、岩矿鉴定、岩相分析、测井相分析等,辅以波阻抗反演及地震相刻画,详细分析了滨浅湖砂坝的沉积特征,建立了理想沉积模式。研究表明:大涝坝地区苏维依组滨浅湖砂坝,垂向上可划分为两段,早期以水体较浅的滨湖砂坝为主,晚期以水体渐深的浅湖砂坝为主。研究区南侧始终发育滨岸砂坝,砂坝均可进一步划分为坝中、坝缘、坝滩微相;研究区中部发育的滨浅湖砂坝,与东部湖岸线近垂直状延伸,受水下隆起控制最为明显,湖泊水体循环和供源体系等发挥了辅助作用。储层成因的明确,对于该区勘探开发方案的制定具有重要指导意义。

As an important type of terrestrial oil and gas reservoir, the shore-shallow lacustrine sand bar is generally parallel to or intersected with the lake shoreline at a low angle. But the Suweiyi Formation in the Dalaoba area presents distinctive spatial distributions characteristics besides the shore-shallow lacustrine depositional features. In order to elaborate the sedimentary characteristics and to establish the ideal sedimentary model of the Suweiyi Formation, on the basis of previous research, such as the detailed core observation, rock-mineral identification, lithofacies description, log facies analysis, wave impedance inversion, seismic facies characterization, and so on, were implemented. The results show that the shore-shallow lacustrine sand bar of the Suweiyi Formation in the Dalaoba area can be vertically divided into two sections. The lower section is dominated by shore lacustrine sand bar formed in shore lake facies, and the upper section is dominated by shallow lacustrine sand bar formed in gradually-deepening shallow lake facies. The shoreland sand bar is consistently developed in the south part of the study area. Both the shore-shallow lacustrine sand bar and the shoreland sand bar can be further divided into the bar-center, the bar-lateral, and the bar-shoal microfacies. The shore-shallow lacustrine sand bar developed in the central area is nearly perpendicular to the eastern lake shoreline. It is speculated that the special space distribution is mainly controlled by the underwater uplift, the lake water circulation and the sediment source. The clarification of the genesis of this kind of reservoir has important guiding significance for the exploration and exploitation program in the study area.